Another idea: Talk to the postal carriers in the area you are interested in.

My wife spoke to our insurance carrier and they had us file a claim.

Lets say its on average 50k per property for united national vs 150k per property for state farmCan some professionals chime in on who there carriers are and what they do?

Also, you will need to talk to your title company to see how the ownership change will affect the title policy.Don't forget to get your property insurance updated as well - some insurance carriers will consider the LLC owned policy as commercial which may cost more.

Finally who is responsible to report the broken lock when in fact the postal carrier (and the thieves) are the only ones aware of it? 

You have to use a carrier that has an early cash value rider to really get the most bang for your buck.

If not, then you can renew with a different carrier and save.  

Did you try to file with your own insurance carrier?  

I see the list of approved USPS mailboxes, but I can’t find anything on how to get the mail carrier access.

I just talked to my mail carrier when he delivered the mail.